JP2000080447A - Low thermal expansion alloy steel excellent in etchability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide low expansion alloy steel free from the generation of defects in etching such as unevenness in stripes causing the reduction of the visibility of a picture in the case of being applied to a shadow mask and capable of etching working of high precision imparting good pore shape. SOLUTION: This alloy is obtd. based on the knowledge that, by controlling the intervals among the dendrite arms of a slab to specified conditions and controlling the distance between Ni-concentrated parts inevitably present at the intervals of the dendrite arms, low thermal expansion alloy steel having excellent etching characteristics can be obtd., and, as to an Fe-Ni alloy contg. 30 to 45 wt.% Ni, the intervals among the dendrite arms cast by a continuous casting method are controlled to <=1,000 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a shadow mask,
Low thermal expansion alloy steel used for various temperature control equipment such as thermostats, especially low expansion alloys with excellent etching characteristics suitable for high definition shadow masks used for computer displays, high-brightness large-screen television CRTs, etc. The present invention relates to steel and a method for manufacturing the same.

[0002]

2. Description of the Related Art Electronic parts such as shadow masks made of alloy thin plates are generally manufactured through etching. Particularly, with respect to shadow masks, the quality of the product depends on the etching speed, the both ends of the hole after etching. Greatly depends on the shape, dimensional accuracy, etc.

[0003] This will be described below using a shadow mask for a cathode ray tube as an example. The shadow mask is used for a cathode ray tube such as a television and a computer display, and generally, a low thermal expansion alloy thin plate rolled to a thickness of about 0.1 to 0.3 mm is used as a material thereof. The shadow mask converts the electron beam emitted from the electron gun,
A specific color tone is given to an image by accurately irradiating a predetermined position on a phosphor screen of a black external light absorbing film supported by a glass body. Therefore, a fine etching hole of about 100 to 300 μm is formed on the entire surface of the shadow mask. Since the entire surface of the mask including the non-opening portion is irradiated with the electron beam, the shadow mask in use is heated over the entire surface and becomes hot.

[0004] Low carbon steel, which has been conventionally used as a material for shadow masks, has a relatively high temperature sensitivity to the volume expansion coefficient, so that when it is heated by irradiation with an electron beam, a thermal expansion phenomenon occurs. The aperture moved and the electron beam could not be irradiated accurately. As a result, the image becomes ambiguous, and a clear image cannot be obtained. For this reason, in recent years, Fe-36% Ni (amber alloy) has been widely used as a material for a high quality shadow mask. Amber alloy has a coefficient of thermal expansion of about 1/1 compared to conventionally used low carbon steel.
Since it is about 0, blurring of the image due to the thermal expansion as described above does not easily occur.

[0005] An Fe-Ni alloy thin plate is manufactured by casting a slab by a continuous casting method, and then performing hot rolling, cold rolling and annealing. After forming an electron beam passage hole by photoetching this alloy thin plate, through the steps of annealing, forming and blackening,
A material for a shadow mask is manufactured. However, the Fe—Ni-based alloy thin plate, which is a material for a shadow mask, has excellent low thermal expansion characteristics, but has poor etching characteristics, and it is difficult to obtain a good hole shape by photoetching. For this reason, poor image sharpness may occur locally due to poor etching.

On the other hand, in recent years, with the enlargement of television screens and the expansion of application of shadow masks to computer displays and the like, the demand for finer images and higher brightness has been further increased. A need has arisen to drill holes for passing electron beams in the mask with higher precision. Conventionally, when manufacturing shadow masks, in order to drill fine holes with high precision in the etching surface, the material material has been improved together with the improvement of the etching technology, but the above-mentioned local characteristics unique to amber alloy It has been difficult to effectively improve the defect of the hole shape caused by the defective etching.

[0007]

The poor etching of the shadow mask is observed as fine linear unevenness in the mask portion along the rolling direction of the alloy thin plate, resulting in "streak unevenness".
is called. Most of these line irregularities are several tens μm to several meters.
It has a width of about m and extends from one side of the mask portion to the other side.
Conventionally, it is known that such streak unevenness occurs due to the segregation of Ni and the segregation of impurities, and several techniques have been proposed to suppress such streak unevenness.

For example, Japanese Patent Application Laid-Open No. Hei 9-176797 discloses that, under a specific component composition, the crystal grain size is adjusted to a crystal grain number of 5.0 or more, which is excellent in etching piercing characteristics, resonance resistance and buckling resistance. Shadow masks have been proposed.
Japanese Patent Application Laid-Open No. 9-143625 proposes a method of suppressing the occurrence of uneven stripes by regulating the difference in the concentration of Si, Mn, and P at the same position as the segregation of Ni. However, it is impossible to obtain high-accuracy etching characteristics only by the refinement of crystal grains and the regulation of the difference in component concentration as in these conventional techniques.

Japanese Patent Publication No. 7-78270 discloses that
1100 ° C for continuous cast slabs with an equiaxed crystal ratio of 30% or less
A method has been proposed in which heating for one hour or more and heating for one hour or more at 950 ° C. or more in a continuous casting slab having an equiaxed crystal ratio of less than 30% are performed to suppress the occurrence of streak unevenness. . However, by simply changing the heating conditions depending on the magnitude of the equiaxed crystal ratio, it is not possible to stably eliminate streak unevenness, particularly in shadow masks for computer displays, which need to drill fine etching holes with high precision. Impossible.

As described above, the prior art cannot completely eliminate etching defects such as uneven stripes, and it is difficult to stably manufacture a high-quality shadow mask that has been required in recent years. Therefore, an object of the present invention is to provide a high-precision etching process with a good hole shape without causing etching defects such as streak unevenness that causes a reduction in image sharpness when applied to a shadow mask. An object of the present invention is to provide a low-expansion alloy steel that can sufficiently meet the demand for high quality masks and the like. Another object of the present invention is to provide a manufacturing method suitable for obtaining such a low expansion alloy steel.

[0011]

Means for Solving the Problems The present inventors have proposed Fe-N
As a result of various investigations on the etching characteristics of the i-type low thermal expansion alloy thin plate, the etching defects such as the above-described streak unevenness were observed, and the morphology of the solidification structure inside the slab elongated during hot rolling and cold rolling, specifically, Have found that it is greatly influenced by the dendrite arm spacing, not by the morphology of the crystal grains in the solidified structure.

That is, the slab of the Fe—Ni alloy is subjected to heating and soaking in a heating furnace, and then hot-rolled. Produces a thick oxide scale, which requires subsequent slab care. Therefore, when the slab is soaked, it is advantageous in terms of the process that the soaking temperature is low and the soaking time is short. However, if the soaking temperature is low, the diffusion of Fe and Ni atoms is not performed sufficiently, so that Fe and Ni
Concentration segregation may remain. Generally, it is necessary to soak at 1200 ° C. or more in order to sufficiently perform the above-described atomic diffusion.

The most problematic in photoetching is the segregation of Fe and Ni described above. Ni is not an element that segregates at the grain boundaries, but is discharged between the main axes of Fe dendrite, that is, between dendrite trees. Therefore, the prior art (for example, Japanese Patent Application Laid-Open No.
No. 6797) found that such a problem of segregation of Fe and Ni could not be improved.

As a result of further studies by the present inventors based on the above findings, the interval between the dendrite arms is adjusted to a specific condition by controlling the cooling rate of the slab and the like, and the interval between the dendrite arms is inevitable. Ni that exists
It has been found that by controlling the distance between the concentrated portions, a low thermal expansion alloy steel having excellent etching characteristics can be produced. In addition, production conditions for obtaining such a low thermal expansion alloy steel were also examined, and found were casting conditions under which the interval between dendrite arms of the slab could be stably set to 1000 μm or less.

The present invention has been made based on such findings, and is characterized by a Fe—Ni alloy containing 30 to 45% by weight of Ni, and a slab dendrite cast by a continuous casting method. 1000 μm between arms
It is a low thermal expansion alloy steel excellent in etching properties characterized by being controlled as follows.

The features of the method for producing a low thermal expansion alloy steel of the present invention are as follows. [1] When a Fe—Ni alloy containing 30 to 45% by weight of Ni is cast by a continuous casting method, the difference ΔT (° C.) between the temperature of the molten steel and the liquidus temperature during the continuous casting is represented by ΔT ≦ 30, and the magnetic flux density B (Gauss) of electromagnetic stirring and the cooling rate V (° C./m
in) that satisfies the following formulas (1) and (2). When 0 ≦ B ≦ 500 2.0−B / 1000 ≦ V (1) When 500 <B 1.5 ≦ V (2)

[2] Ni: F containing 30 to 45% by weight
When casting an e-Ni alloy by a continuous casting method, the difference ΔT (° C.) between the temperature of the molten steel and the liquidus temperature during the continuous casting is set to 30 <ΔT ≦ 50, and the electromagnetic force during the continuous casting is set. Magnetic flux density of stirring B
(Gauss) and the cooling rate V (° C./min)
A method for producing a low-thermal-expansion alloy steel having excellent etching properties, which satisfies the relationship of equation (4). When 0 ≦ B ≦ 500 2.2−B / 1000 ≦ V (3) When 500 <B 1.7 ≦ V (4)

Here, the dendrite arm interval defined in the present invention is defined as follows. FIG. 1 shows a dendrite in the case of a so-called columnar crystal in which the dendrite of a slab has grown in a direction. FIG. 1 (a) is a schematic diagram of a dendrite having a slab cross section, and FIG. 1 (b) is a diagram of FIG. It is a graph which shows the Ni concentration distribution in the part which followed the arrow line. FIG. 2 shows the dendrite in the case of a so-called equiaxed crystal in which the directionality of the dendrite of the slab is random,
FIG. 4A is a schematic diagram of a dendrite having a slab cross section, and FIG. 4B is a graph showing a Ni concentration distribution in a portion along an arrow line in FIG. In the present invention, FIG.
The interval between adjacent peak portions of the Ni concentration distribution shown in (b) is defined as a dendrite arm interval.

In general, the interval between dendrite arms is not constant in the slab thickness direction, but tends to increase toward the center in the slab thickness direction. However, in the present invention, the maximum dendrite arm interval (usually, １ ／ of the slab thickness direction) is used. The distance between the dendrite arms in the vicinity) needs to be 1000 μm or less.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below. The low thermal expansion alloy steel of the present invention is an Fe-Ni alloy containing 30 to 45% by weight of Ni. It has expandability. By using such an Fe—Ni alloy, the average thermal expansion coefficient at room temperature to 100 ° C. is 2.0 × 1/1.
0 6 ^/ ° C. it is possible to obtain a low thermal expansion alloy sheet such that follows. In the low-thermal-expansion alloy steel of the present invention, Co may be added as an element that partially replaces Ni as long as desired low-thermal-expansion characteristics are obtained.

The low-thermal-expansion alloy steel of the present invention contains elements other than Ni and Fe, as long as the effects of the present invention are not impaired.
For example, Si, Mn, B, N, O, etc. may be contained,
About these contents, Si: 0 to 0.07% by weight
(However, no addition is included), Mn: 0 to 0.5% by weight (including no addition), B: 0 to 0.02% by weight (however, no addition is included) , N: 0 to 0.00
5% by weight (including the case of no addition), O: 0 to 0.
It is preferable to limit the amount to a range of 01% by weight (including the case where no additive is added).

[0022] Si can be added as a deoxidizing element of molten steel, but if added excessively, it will be concentrated in the surface layer of the plate during the blackening treatment, impeding the formation of a uniform black oxide film. Therefore, the content of Si is preferably set to 0.07% by weight or less.
Mn is a useful element in securing good hot workability, but when added excessively, it lowers the etching property, and in the blackening treatment, it concentrates on the surface layer of the plate, forming a uniform black oxide film. Inhibits. For this reason, Mn is preferably set to 0.5% by weight or less.

B has the effect of improving hot workability and suppressing scale formation. However, if added excessively, it will be concentrated in the surface layer of the plate during the blackening treatment, impeding the formation of a uniform black oxide film. Therefore, B is preferably set to 0.02% by weight or less. Since N causes deterioration in press workability and etching property, it is preferably set to 0.005% by weight or less. O inhibits the growth of crystal grains during softening annealing before pressing and deteriorates press formability.
It is preferable to set the following. In addition, it does not prevent the alloy from containing trace amounts of other elements such as unavoidable impurities other than the above.

In the low thermal expansion alloy steel of the present invention, the interval between dendrite arms of a slab cast by a continuous casting method is one.
The low-thermal-expansion alloy sheet is characterized by being controlled to 000 μm or less, and is manufactured through a cold rolling and annealing process after heating and equalizing a slab having such a controlled dendrite arm spacing and hot rolling. You. By shortening the dendrite arm spacing of the slab as defined by the present invention, it becomes possible to effectively diffuse the Ni atoms segregated between the dendrite trees with a short soaking time, and as a result, the Ni enrichment of the dendrite arm spacing It is possible to eliminate etching defects such as uneven stripes caused by the portions.

FIG. 3 shows the effect of the slab dendrite arm spacing on the etching characteristics in relation to the slab soaking time (slab soaking temperature: 1300 ° C.). In the evaluation of the etching characteristics, no abnormality was found in the shape or interface of the hole after the etching, and the dimensional accuracy was ± 2%.
The following are indicated by “○”, and the other (the one having a problem in etching property) are indicated by “×”. According to FIG. 3, in a slab having a dendrite arm interval of 1000 μm or less, a soaking heat treatment at a soaking temperature of 1300 ° C. for about 20 hours or more causes a Ni-enriched portion inevitably existing in the dendrite arm interval. It is shown that uneven stripes are eliminated and excellent etching characteristics can be obtained. In contrast, the dendrite arm spacing is 1000
In the case of a slab having a thickness of more than μm, unevenness due to the Ni-enriched portion in the dendrite arm interval cannot be eliminated even if the soaking treatment is performed for a long time, and the etching characteristics are poor.

The interval between the dendrite arms of the slab can be adjusted, for example, by controlling the cooling rate of the slab during casting, or by controlling the dendrite crystallization by electromagnetic stirring or the like in the mold. In particular, the interval between the dendrite arms tends to depend on the cooling rate of the slab, and it is effective to increase the cooling rate of the slab during casting to shorten the interval between the dendrite arms.
In addition, in order to shorten the dendrite interval of the slab, it is necessary to lower the casting temperature of the molten metal during slab casting as much as possible, and furthermore, to carry out electromagnetic stirring controlled to an appropriate strength to form fine equiaxed dendrites. It is also effective to put out.

In order to obtain the low thermal expansion alloy steel of the present invention,
The alloy steel is melted in a converter, electric furnace, or other molten steel smelting furnace, and the slab is cast by a continuous casting method. Usually, the slab thickness is about 120 to 500 mm. Then, in order to obtain a desired dendrite arm interval of the slab, for example, the cooling rate is controlled by adjusting the casting temperature of the molten metal during slab casting, adjusting the cooling conditions in the secondary cooling zone, or in the mold. Fine equiaxed dendrite is crystallized by performing electromagnetic stirring controlled to an appropriate strength, or the like, or by appropriately combining these.

Hereinafter, preferable production conditions for obtaining the low thermal expansion alloy steel of the present invention will be described. The effects of the cooling rate, the strength of electromagnetic stirring, the casting temperature of the molten metal, etc. on the size of the dendrite arm spacing during slab casting differ from one another. Slabs with dendrite arm spacing of 1000 μm or less can be manufactured regardless of their solidification structure,
For example, even when the solidification structure is columnar, the cooling rate is set to be relatively high to make the dendrite arm spacing 100
It can be reduced to 0 μm or less. On the other hand, when the solidified structure is equiaxed, it is easy to make the dendrite arm spacing 1000 μm or less even if the cooling rate is somewhat low.
In order to relatively easily and stably produce a slab of 000 μm or less, it is advantageous to make the solidified structure equiaxed. The present inventors have found that the production conditions suitable for reducing the dendrite arm spacing of the cast slab to 1000 μm or less, particularly the production suitable for reducing the dendrite arm spacing to 1000 μm or less by making the solidification structure equiaxed. I found the condition.

A lower molten metal casting temperature is advantageous for equiaxed crystallization of the solidified structure, and a difference ΔT (degree of molten steel superheating) between the molten metal casting temperature (molten steel temperature during casting) and the liquidus temperature is 50%.
If the temperature exceeds ℃, it is difficult to achieve equiaxed crystallization of the solidified structure. Therefore, it is preferable that ΔT be in a range not exceeding 50 ° C. Further, since the influence of the solidified structure on the equiaxed crystallization varies depending on ΔT, the case of ΔT ≦ 30 and the case of 30 <30
The production conditions were examined separately for the case of ΔT ≦ 50, and as a result, the dendrite arm spacing of the slab was stably 1000 μm by adopting the following production conditions.
It turns out that we can do the following.

First, when the difference ΔT between the molten steel temperature and the liquidus temperature during continuous casting is ΔT ≦ 30, the magnetic flux density B
When (Gauss) is 0 ≦ B ≦ 500, the relationship between the magnetic flux density B (Gauss) of the electromagnetic stirring and the cooling rate V (° C./min) is expressed by the following equation (1): 2.0−B / 1000 ≦ V By satisfying (1), the magnetic flux density B
When (Gauss) is 500 <B, the relationship between magnetic flux density B (Gauss) of electromagnetic stirring and cooling rate V (° C./min) is as follows.
By satisfying the expression (2), 1.5 ≦ V (2), the interval between dendrite arms of the slab to be cast can be made 1000 μm or less.
Here, the magnetic flux density B (Gauss) is the magnetic flux density at the time of air core (the same applies hereinafter).

When the difference ΔT between the molten steel temperature and the liquidus temperature during continuous casting is 30 <ΔT ≦ 50, and when the magnetic flux density B (Gauss) of the electromagnetic stirring is 0 ≦ B ≦ 500, the electromagnetic stirring is not performed. The relationship between the magnetic flux density B (Gauss) and the cooling rate V (° C./min) satisfies the following expression (3): 2.2−B / 1000 ≦ V (3) Density B
When (Gauss) is 500 <B, the relationship between magnetic flux density B (Gauss) of electromagnetic stirring and cooling rate V (° C./min) is as follows.
By satisfying the expression (4), 1.7 ≦ V (4), the interval between dendrite arms of the slab to be cast can be made 1000 μm or less.

Therefore, preferable production conditions of the low thermal expansion alloy steel of the present invention are as follows: when the difference ΔT (° C.) between the temperature of the molten steel and the liquidus temperature during continuous casting is ΔT ≦ 30, Magnetic flux density B (Gauss) of stirring and cooling rate V
(° C./min) preferably satisfies the relationship of the following expressions (1) and (2). When 0 ≦ B ≦ 500 2.0−B / 1000 ≦ V (1) When 500 <B 1.5 ≦ V (2)

When the difference ΔT (° C.) between the temperature of the molten steel and the liquidus temperature during continuous casting is 30 <ΔT ≦ 50, the magnetic flux density B (Gauss) and the cooling rate V of electromagnetic stirring during continuous casting are set.
(° C./min) preferably satisfies the relationship of the following expressions (3) and (4). When 0 ≦ B ≦ 500 2.2−B / 1000 ≦ V (3) When 500 <B 1.7 ≦ V (4)

After the cast slab is heated and soaked,
Although the slab is subjected to hot rolling, high-temperature soaking is indispensable in hot rolling the slab in order to diffuse Ni atoms segregated between dendrite trees. This is because the diffusion coefficient of Ni atoms in Fe is very small as compared with other mixed atoms, and soaking at a temperature such as that performed with ordinary carbon steel is insufficient. The present inventors modeled the degree of diffusion of Ni atoms in accordance with the soaking time, and found that under the soaking conditions around 1300 ° C. for a slab in which the dendrite arm spacing was controlled to 1000 μm or less, the diffusion of Ni atoms was necessary. The result was that the required time was about 20 hours or more. That is, if the soaking treatment is performed at 1300 ° C. × 20 hours or more, Ni segregation in the slab can be sufficiently reduced, and streak unevenness caused by Ni-enriched portions inevitably existing in the dendrite arm interval can be effectively eliminated. I understood.

However, if the soaking treatment is performed for 50 hours or more, the amount of surface layer scale of the slab increases, so that the cost and process burden of slab care increase, and the energy loss of the heating furnace also increases. Is preferably within 50 hours. The hot-rolled alloy steel is subjected to at least one cold rolling and annealing treatment according to a conventional method to produce an alloy thin plate.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an alloy thin plate for a shadow mask is manufactured and subjected to photo-etching will be described below. A slab was cast by a continuous casting method using an Fe—Ni alloy having a component composition shown in Table 1. In the casting of the slab, the spacing between the dendrite arms of the slab was adjusted by controlling the cooling rate and the like and performing electromagnetic stirring as needed. Table 2 and Table 3
And then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.0 to 4.0 mm. Further, cold rolling and annealing at 700 ° C. or more were performed 1 to 4 times to obtain a sheet thickness of 0.0
Alloy thin plates of 9 to 0.25 mmn were produced.

These low thermal expansion alloy thin plates were etched to obtain alloy thin plates for shadow masks. In these alloy thin plates for shadow masks, no abnormality was found in the shapes and interfaces of the holes after etching, and the dimensional accuracy was ±
Those that are 2% or less (those that can meet the requirements for high quality and high luminance) are marked with “O”, and those other than that (there is a problem with the etching properties and the requirements for high quality and high luminance cannot be met) ) Was evaluated as “×”, and the etching property was evaluated.

The results of the etching property evaluation were evaluated based on the slab casting conditions (superheat degree of molten steel, cooling rate, and magnetic flux density of electromagnetic stirring),
Tables 2 and 3 show the dendrite shape, dendrite arm spacing, and slab soaking conditions. According to Tables 2 and 3, it is found that the alloy material for a shadow mask of the present invention can obtain excellent etching characteristics as compared with the comparative example.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

As described above, the low-thermal-expansion alloy steel of the present invention exhibits excellent etching characteristics. Therefore, when it is applied to a shadow mask, etching defects such as uneven stripes which cause a reduction in image sharpness are reduced. It is possible to perform high-precision etching with no holes and good hole shape, and it is possible to produce a high-quality, high-brightness shadow mask that cannot be produced by the conventional technology. Further, according to the manufacturing method of the present invention, such a slab of low thermal expansion alloy steel can be stably manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing columnar dendrites grown with directionality and their Ni concentration distributions.

FIG. 2 is an explanatory diagram showing equiaxed dendrites having random orientations and their Ni concentration distributions.

FIG. 3 is a graph showing the influence of the dendrite arm spacing of the slab on the etching characteristics in relation to the slab soaking time.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 29/07 H01J 29/07 A (72) Inventor Tomoaki Hyodo 1-2-1 Marunouchi 1-chome, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Tamako Ariga 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd.

Claims (4)

[Claims] 1. Fe containing 30 to 45% by weight of Ni
-A low-thermal-expansion alloy steel excellent in etching property, characterized in that a distance between dendrite arms of a slab cast by a continuous casting method is controlled to 1000 µm or less, which is a Ni-based alloy. 2. A low-thermal-expansion alloy steel sheet made of the slab according to claim 1 and having excellent etching properties. 3. Ni: Fe containing 30 to 45% by weight.
When casting a Ni-based alloy by a continuous casting method, the difference ΔT (° C.) between the temperature of the molten steel and the liquidus temperature during the continuous casting is set to ΔT ≦ 30, and the magnetic flux of electromagnetic stirring during the continuous casting is set. Density B
(Gauss) and the cooling rate V (° C./min)
A method for producing a low thermal expansion alloy steel having excellent etching properties, which satisfies the relationship of the formula (2). When 0 ≦ B ≦ 500 2.0−B / 1000 ≦ V (1) When 500 <B 1.5 ≦ V (2) 4. Fe containing 30 to 45% by weight of Ni.
When casting a Ni-based alloy by a continuous casting method, the difference ΔT (° C.) between the temperature of the molten steel and the liquidus temperature during the continuous casting is set to 30 <ΔT ≦ 50, and electromagnetic stirring during the continuous casting is performed. Magnetic flux density B
(Gauss) and the cooling rate V (° C./min)
A method for producing a low-thermal-expansion alloy steel having excellent etching properties, which satisfies the relationship of equation (4). When 0 ≦ B ≦ 500 2.2−B / 1000 ≦ V (3) When 500 <B 1.7 ≦ V (4)